SMCJ78 Transient Voltage Suppressor Diode - Equivalent & Substitute Parts

Part Overview

The SMCJ78 is a unidirectional Zener transient voltage suppressor (TVS) diode manufactured by Littelfuse Inc., designed for general-purpose overvoltage protection in surface-mount applications. The device features a 78V reverse standoff voltage with 132.3V maximum clamping voltage and 11.9A peak pulse current capability in a DO-214AB (SMC) package. The SMCJ78 is classified as obsolete, necessitating identification of active equivalent and substitute parts that maintain electrical and mechanical compatibility for new designs and production continuity.

Key Parameters

Parameter	Value	Unit
Voltage - Reverse Standoff (Typ)	78	V
Voltage - Breakdown (Min)	82.13	V
Voltage - Clamping (Max) @ Ipp	132.3	V
Current - Peak Pulse (10/1000µs)	11.9	A
Power - Peak Pulse	1500	W
Operating Temperature Range	-55 to 150	°C
Package / Case	DO-214AB, SMC	—
Mounting Type	Surface Mount	—
Type	Zener	—
Unidirectional Channels	1	—

Substitute Part Grouping Explanation

Substitute parts for the SMCJ78 are grouped based on strict electrical and mechanical compatibility criteria. The primary substitution parameters are:

Voltage - Reverse Standoff: 78V (fixed across all substitutes)
Voltage - Breakdown (Min): 82.13V to 86.7V (acceptable range)
Package / Case: DO-214AB, SMC (identical mechanical form factor)
Mounting Type: Surface Mount (identical)
Type: Zener, Unidirectional (identical)
Unidirectional Channels: 1 (identical)
RoHS Status: ROHS3 Compliant (all substitutes)

Substitutes are divided into two electrical categories:

Category A: Standard Performance (11.4A to 11.9A Peak Pulse Current, 1500W) SMCJ78A, SMCJ78A-13-F, SMCJ78A-TP, SMCJ78AE3/TR13, SMCJ78E3/TR13

Category B: Enhanced Performance (22.8A Peak Pulse Current, 3000W) SMLJ78A, SMLJ78A-TP, SMLJ78AE3/TR13

Parameter Comparison

Part Number	Manufacturer	Voltage - Reverse Standoff (V)	Voltage - Breakdown Min (V)	Voltage - Clamping Max @ Ipp (V)	Current - Peak Pulse (A)	Power - Peak Pulse (W)	Operating Temp (°C)	Package	Product Status
SMCJ78	Littelfuse Inc.	78	82.13	132.3	11.9	1500	-55 to 150	DO-214AB, SMC	Obsolete
SMCJ78A	MDD	78	86.7	126	11.9	1500	-50 to 150	DO-214AB, SMC	Active
SMCJ78A-13-F	Diodes Incorporated	78	86.7	126	11.4	1500	-55 to 150	DO-214AB, SMC	Active
SMCJ78A-TP	Micro Commercial Co	78	86.7	126	11.9	1500	-55 to 175	DO-214AB, SMC	Active
SMCJ78AE3/TR13	Microchip Technology	78	86.7	126	11.4	1500	-65 to 150	DO-214AB, SMC	Active
SMCJ78E3/TR13	Microchip Technology	78	86.7	139	10.8	1500	-65 to 150	DO-214AB, SMC	Active
SMLJ78A	Bourns Inc.	78	86.7	126	22.8	3000	-55 to 150	DO-214AB, SMC	Active
SMLJ78A-TP	Micro Commercial Co	78	86.7	126	22.8	3000	-55 to 175	DO-214AB, SMC	Active
SMLJ78AE3/TR13	Microchip Technology	78	86.7	126	22.8	300	-55 to 150	DO-214AB, SMC	Active

Engineering Selection Recommendations

For Direct Replacement (Standard Performance Category): SMCJ78A-TP (Micro Commercial Co) is the primary recommendation for direct substitution. It maintains identical electrical specifications (78V standoff, 126V clamping, 11.9A peak pulse, 1500W power) with extended operating temperature range (-55 to 175°C) and active product status. Tape & Reel packaging ensures production continuity.

Alternative Standard Performance Options: SMCJ78A (MDD) and SMCJ78AE3/TR13 (Microchip Technology) are functionally equivalent with active status and ROHS3 compliance. SMCJ78AE3/TR13 offers the widest operating temperature range (-65 to 150°C).

For Enhanced Dissipation Requirements: SMLJ78A-TP (Micro Commercial Co) and SMLJ78A (Bourns Inc.) provide doubled peak pulse current (22.8A) and power rating (3000W) while maintaining identical voltage parameters and DO-214AB packaging. These are suitable for applications requiring higher transient energy absorption.

All recommended substitutes carry ROHS3 compliance and MSL 1 (Unlimited) moisture sensitivity rating, matching the original SMCJ78 specifications.

Frequently Asked Questions (FAQ)

Q: Can SMCJ78A directly replace SMCJ78 in existing designs? A: Yes. SMCJ78A maintains the same 78V reverse standoff voltage, DO-214AB package, and 1500W power rating. Clamping voltage is slightly lower (126V vs 132.3V), which is within acceptable tolerance for general-purpose overvoltage protection. All active substitutes are pin-compatible and footprint-compatible.

Q: What is the difference between SMCJ78A and SMLJ78A? A: Both maintain identical voltage parameters (78V standoff, 126V clamping). The primary difference is peak pulse current and power dissipation: SMCJ78A handles 11.9A at 1500W, while SMLJ78A handles 22.8A at 3000W. SMLJ78A is suitable for higher-energy transient events. Both use the same DO-214AB package.

Q: Are all substitutes available in Tape & Reel packaging? A: Most substitutes are available in Tape & Reel (TR) format for production use. SMLJ78A-TP is supplied in Bulk packaging. Verify packaging specification with supplier documentation before procurement.

Q: What is the significance of the temperature range difference between substitutes? A: Operating temperature range affects device reliability in extreme environments. SMCJ78A-TP and SMLJ78A-TP extend to 175°C (vs 150°C standard), providing margin for high-temperature applications. SMCJ78AE3/TR13 extends to -65°C for low-temperature environments. Select based on application thermal requirements.

Q: Do all substitutes meet RoHS3 compliance? A: Yes. All listed substitutes carry ROHS3 Compliant status, matching the original SMCJ78 specification. Moisture sensitivity level is MSL 1 (Unlimited) across all parts.

Q: Can SMCJ78E3/TR13 be used as a direct substitute? A: SMCJ78E3/TR13 is electrically compatible with identical voltage parameters but features higher clamping voltage (139V vs 132.3V) and slightly lower peak pulse current (10.8A vs 11.9A). It is suitable for applications where higher clamping voltage is acceptable or beneficial.

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